Screening for depressive symptoms: Validation of the CES-D scale in a multi-ethnic group of patients with diabetes in Singapore

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1 Diabetes Care Publish Ahead of Print, published online March 25, 2008 Screening for depressive symptoms: Validation of the CES-D scale in a multi-ethnic group of patients with diabetes in Singapore Stahl D*MD, Sum CF*FRCPE, Lum SS#BA, Liow PS*MMed(Psychiatry) Chan YH@PhD Verma S#MD Chua HC# MMed(Psychiatry) Chong SA# MMed(Psychiatry) *Diabetes Centre, Medicine, Alexandra Hospital, Singapore # Clinical Research, Institute of Mental Health, Unit, Yong Loo Lin, National University of Singapore Corresponding Author: Sum CF Diabetes Centre, Alexandra Hospital, 378 Alexandra Road, Singapore chee_fang_sum@alexhosp.com.sg Received for publication 19 October 2007 and accepted in revised form 26 February Copyright American Diabetes Association, Inc., 2008

2 ABSTRACT Objective: We determined the reliability and validity of the CES-D, against the DSM IV based diagnostic inventory, SCAN, in a multiethnic sample of adult subjects with diabetes attending a diabetes centre in Singapore. Research Design & Methods: 522 subjects (74.7% Chinese, 11.1% Malay, 14.2% Indian) completed culturally adapted versions of the CES-D. 291 subjects were administered the SCAN inventory. Results & Conclusions: The CES-D proved to be a reliable instrument for identifying patients with depressive symptoms in the multiethnic setting of this study. The CES-D (cut-off score 16) showed high NPV of more than 90% in all three ethnic groups. The prevalence of depressive symptoms (CES-D) and depression (SCAN) was significantly different between the Chinese & Indians (CES-D 27.4% vs 43.2%) (p=0.006); (SCAN 15.0% vs 31.1%) (p=0.01).

3 A recent meta-analysis showed that diabetes doubles the odds of comorbid depression (1). Co-morbid depression is associated with adverse diabetes outcomes, increased health-care use and expenditure. Even though effective treatment for depression in patients with diabetes is available, there is evidence that individuals with depression are under-diagnosed and under-treated. Screening for depression is therefore recommended in diabetes guidelines. The Center for Epidemiologic Studies Depression (CES-D) scale has been used in patients with different disorders including diabetes. However, less is known about its use in depression screening across diverse ethnic groups of patients with diabetes (2-3). Singapore has three main ethnic groups (Chinese, Malays, Indians) and a relatively high prevalence of diabetes (8.2%) (4). An earlier community based study indicated that the prevalence of depression amongst adult Singaporean Chinese was 5.6%, Malays 4.1% and Indians 8.6% (5). The aim of this study was to validate culturally adapted versions of the CES-D in different languages, in a multiethnic group of patients attending a diabetes centre in Singapore. RESEARCH DESIGN & METHODS Adult outpatients attending the Alexandra Hospital Diabetes Centre who had their annual complications screen performed within the last six months were invited to participate in this study. After informed consent, sociodemographic and clinical data were collected and depressive symptoms were assessed for all participants using the CES-D. Participants were also invited to a diagnostic interview using the Schedule for Clinical Assessment in Neuropsychiatry (SCAN) within the same week. The CES-D is a 20-item self-report depressive symptom based scale for depression (6). Each participant chose from English, Chinese (3) or Malay versions of the scale according to his language proficiency and cultural background. The Malay version of the CES-D was developed by using backtranslation technique (7). SCAN uses a diagnostic inventory approach to assess and classify the psychopathology and behavior associated with major psychiatric syndromes in adults, according to DSM-IV, and has been found to be generally acceptable and reliable across cultures and settings (8). It has been previously used in Singapore (9). The interrater reliability of the multilingual SCAN interviewers was good (kappa 0.63). Statistical analyses were performed using SPSS Reliability of the CES-D was verified using Cronbach alpha. To determine the screening performance of the CES-D and to identify optimal cut-off scores, receiver operating characteristic curve (ROC) analysis was used. Statistical significance was set at p < RESULTS 537 subjects (mean age y, Type 1 diabetes: 3.5%) agreed to participate in the study. 72.6% were Chinese, 10.8% Malay, 13.8% Indian and 2.8 % of other ethnicity (Caucasian, Eurasian, Japanese etc). The non-participation rate was 6.1%. Only data from 522 Chinese, Malay and Indian subjects who completed the CES-D were further analyzed. 291 subjects agreed to SCAN interview. Socio-economic and clinical parameters (data not shown) between those who completed both CES-D and SCAN and those who completed the CES-D only, were not different. Cronbach s coefficient alpha was 0.72(Chinese); 0.70(Malay); and 0.79(Indian). The AUC values between ethnic groups were not statistically different. Using a cut-off score of 16, the NPV >90% across all ethnic

4 groups. Only three participants (two Malay, one Chinese), who scored less than 16 with the CES-D, were categorized by SCAN as having mild depressive disorder (Table 1). The proportion of people who had CES- D>16; as well as the proportion fulfilling SCAN criteria for clinical depression was different between the Chinese and Indian ethnic groups (CES-D 27.4% vs 43.2%) (p=0.006); (SCAN 15.0% vs 31.1%) (p=0.01) CONCLUSIONS The internal consistency of a scale is as much a characteristic of the population in which it is utilized, as it is of the scale itself. The internal consistency of the CES-D has not been previously assessed in a multiethnic group of patients with diabetes. Our study demonstrates that the CES-D is a reliable scale for our multiethnic patient sample. This study, together with others (1, 10), demonstrates that the prevalence of depression using a depressive symptom approach, as in CES-D; differs from the prevalence of depression using a diagnostic inventory approach as in SCAN. However the high negative predictive value of the CES-D (>90% in all ethnic groups) provides confidence in the CES-D as a screening tool for clinical depression. It might be argued that short questionnaires such as the CES-D assess depressive symptoms rather than clinical depression. Fisher et al in a study on a multiethnic North American sample, has suggested that a high score on the CES-D in people with diabetes may reflect difficulty in coping with a demanding chronic disease (10). In any case, several studies utilizing such scales to study depression have documented the negative effect of depressive symptoms in patients with diabetes, and the benefit of treatment of depressive symptoms on diabetes control, providing empiric evidence for the direct clinical utility of scales such as the CES-D over and above that of being merely a screening tool for clinical depression. Hence patients who test positive on the CES-D and negative on the SCAN may still benefit from increased attention to their psychosocial needs. Our study suggests that the CES-D scale and its culturally adapted versions are reliable instruments to help identify subjects with depressive symptoms in a multiethnic group of patients with diabetes. The high NPV of the CES-D in our sample makes it a valuable screening tool for clinical depression. Hence utilizing the CES-D in our setting is likely to facilitate streamlining of resources to cater to the individual patient s psychosocial needs. There are significant differences in the prevalence of depressive symptoms and depression amongst the different ethnic groups. Ethno-cultural differences may contribute to these differences, and analysis of this possibility will be the subject of future reports.

5 REFERENCES 1. Anderson RJ, Freedland KE, Clouse RE, Lustman PJ: The prevalence of comorbid depression in adults with diabetes: a meta-analysis. Diabetes Care 24: , De Groot M, Pinkerman B, Wagner J, Hockman E: Depression Treatment and Satisfaction in a multicultural sample of type 1 and type 2 diabetic patients. Diabetes Care 29: , Zhang J, Norvilitis J M: Measuring Chinese psychological well-being with western developed instruments. J Pers Assess 79: , NHS,2004.MinistryofHealth,Singapore. 5. Chua HC, Lim L, Ng TP, Lee T, Mahendran R, Fones C, Kua EH: The prevalence of psychiatric disorders in Singapore adults. Annals Academy of Medicine 33 (suppl 5): 1047/MPC, Radloff LS: The CES-D Scale: A self report depression scale for research in the general population. Applied Psychological Measurement 1: , Guillemin F, Bombardier C, Beaton D: Cross-cultural adaptation of health-related quality of life measures. A literature review and proposed guidelines. J Clin Epidemiol 46: , Brugha T S, Nienhuis F, Bagchi D, Smith J, Meltzer H: The survey form of SCAN: the feasibility of using experienced lay survey interviewers to administer a semi-structured systematic clinical assessment of psychotic and non-psychotic disorders. Psychol Med 29: , Lim L, Ng T P, Chua H C, Chiam P C, Won V, Lee T, Fones C, Kua E H: Generalised anxiety disorder in Singapore: prevalence, co-morbidity and risk factors in a multi-ethnic population. Soc Psychiatry Psychiatr Epidemiol 40: , Fisher L, Skaff MM, Mullan JT, Arean P, Mohr D, Masharani U, Glasgow R, Leurencin G. Clinical Depression Versus Distress Among Patients with Type 2 Diabetes. Diabetes Care 30: , 2007

6 TABLE 1. ROC analysis of CES-D versus SCAN (cutoff score 16); and prevalence of depressive symptoms (CES-D) and depression (SCAN) in different ethnic groups. C: Chinese; M: Malay; I: Indian. AUC: Area Under Curve; PPV: Positive Predictive Value; NPV: Negative Predictive Value C (n=207) M (n=39) I (n=45) AUC Sensitivity 96.8% 66.7% 100% Specificity 67.6% 60.6% 64.5% PPV 34.5% 23.5% 56.0% NPV 99.2% 90.9% 100% C (n=390) M (n=58) I (n=74) CES-D 107 (27.4%) 21 (36.2%) 32 (43.2%)* Confidence Interval % % % C (n=207) M (n=39) I (n=45) SCAN 31 (15.0%) 6 (15.4%) 14 (31.1%)* Confidence Interval % % % * C vs I p<0.05